Heat pump operation method and heat pump system

ABSTRACT

A heat pump operation method includes: obtaining, on a per time unit basis, an amount of the power generated by the power generation device, an amount of the power consumed by the electric load, and surplus power which is a difference between the generated power and the load power; and controlling operation of the heat pump to cause the heat pump to generate heat using power adjusted to follow a per time unit increase or decrease in the surplus power. In the controlling, when an amount of change in the surplus power remains greater than a predetermined threshold value for a given period of time extending back from a present time, an extent to which the power consumed by the heat pump follows the surplus power is reduced.

TECHNICAL FIELD

The present invention relates to a heat pump system including a powergeneration device such as a photovoltaic device and a device whichconsumes power such as a heat pump.

BACKGROUND ART

Power generation devices, such as solar or wind power generationdevices, are devices designed to generate power. A photovoltaic devicegenerates power by transforming solar energy into electricity andsupplies the power to a home as a natural source of energy. The amountof power generated by a photovoltaic device constantly fluctuates withweather and meteorological conditions.

A heat pump hot water supply device heats a refrigerant by absorbingheat from the atmosphere and compressing the refrigerant usingelectricity. The heat is then transferred to the water via a heatexchanger, creating hot water. The heat pump hot water supply deviceuses less energy than a conventional electric hot water heater.

A heat pump hot water supply system including a power generation deviceincludes a combination of the above devices, and supplies a consumerwith power and heat. An example of this type of conventional heat pumphot water supply system including a power generation device is disclosedin Patent Literature (PTL) 1.

PTL 1 discloses a heat pump hot water supply system which obtainsweather forecast information from a server using a weather informationobtaining unit. When the obtained information meets a predeterminedcondition, the heat pump hot water supply system switches to usephotovoltaic power to heat the water in the CO2 heat pump hot watersupply device instead of late night power from a commercial powersource. Operating using power harnessed from natural energy allows for apower efficient, low-energy electric heat pump hot water supply devicewhich can reduce electricity costs.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2008-2702

[PTL 2] Japanese Unexamined Patent Application Publication No.2006-158027

SUMMARY OF INVENTION Technical Problem

However, with the techniques disclosed in PTL 1, reverse power isgenerated when the power consumption of the heat pump hot water supplysystem drops below the generated amount of photovoltaic power. As aresult, there is a possibility that the power grid will become unstable.

The present invention was conceived to solve the above-described problemand aims to provide a heat pump operation method and heat pump systemwhich contribute to the stabilization of the power grid by reducingreverse power without sacrificing economics.

Solution to Problem

The heat pump operation method according to an aspect of the presentinvention is a heat pump operation method for use in a system whichincludes a power generation device, an electric load which operatesusing power generated by the power generation device, and a heat pumpwhich generates heat using the power generated by the power generationdevice. Specifically, the heat pump operation method includes:obtaining, on a per time unit basis, generated power which is an amountof the power generated by the power generation device, load power whichis an amount of the power consumed by the electric load, and surpluspower which is a difference between the generated power and the loadpower; and controlling operation of the heat pump to cause the heat pumpto generate heat using power adjusted to follow a per time unit increaseor decrease in the surplus power. In the controlling, when an amount ofchange in the surplus power remains greater than a predeterminedthreshold value for a given period of time extending back from a presenttime, an extent to which the power consumed by the heat pump follows thesurplus power is reduced.

It is to be noted that general or specific embodiments may be realizedas a system, method, integrated circuit, computer program, storagemedia, or any elective combination thereof.

Advantageous Effects of Invention

With the present invention, a small amount of reverse flow or purchaseof power is permitted in exchange for the prevention of rapidfluctuations in heat pump load power, which is achieved by reducing theextent to which the power consumed by the heat pump follows the surpluspower in a period of rapid change in surplus power, resulting in stableoperation of the heat pump.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram outlining the processes performed by the heat pumphot water supply system according to the first embodiment of the presentinvention.

FIG. 2 is a diagram showing the configuration of the heat pump hot watersupply system according to the first embodiment of the presentinvention.

FIG. 3 is a diagram showing the configuration of the heat pump hot watersupply device in detail.

FIG. 4 is an example of a first control table.

FIG. 5 is an example of a second control table.

FIG. 6 is a diagram showing the flow of data with respect to the heatpump (HP) control device according to the first embodiment.

FIG. 7 is a block diagram showing the functions of the HP control deviceaccording to the first embodiment.

FIG. 8 is an example of a surplus power record.

FIG. 9 is a flowchart of operation processes performed by the HP controldevice and a heat pump control unit.

FIG. 10 is a flowchart of processes performed by the HP control devicerelated to the calculation of a power consumption command value.

FIG. 11 is a flowchart of control parameter calculation processesperformed by the heat pump control unit.

FIG. 12A is an example of input information.

FIG. 12B is an example of a second control table.

FIG. 13A shows a result of the first linear interpolation.

FIG. 13B shows a result of the second linear interpolation.

FIG. 14 illustrates the relationship between the change in surplus powerand the calculated power consumption command value.

FIG. 15 is a flowchart of other processes performed by the HP controldevice related to the calculation of power consumption command values.

FIG. 16 is a graph illustrating a situation when “yes” is determined inS1207 in FIG. 15.

FIG. 17 is a graph illustrating a situation when “no” is determined inS1207 in FIG. 15.

DESCRIPTION OF EMBODIMENTS Underlying Knowledge Forming Basis of thePresent Invention

With the conventional heat pump hot water supply system disclosed in PTL1, an amount of surplus power, which is calculated from the constantlyfluctuating amount of power generated by the photovoltaic device and theelectric load of the consumer, is not taken into account in thedetermination of the power to be consumed by the heat pump hot watersupply device. As the number of homes generating surplus power increaseswith the growing prevalence of photovoltaic power generation, thevoltage of a power grid will increase when reverse power issimultaneously generated, causing the power grid to become unstable.Moreover, the consumer, who is located on the downstream side of thepower grid, cannot flow reverse power when the voltage of the power gridis high, so the output thereof must be inhibited, causing the surpluspower generated by the photovoltaic device to go to waste.

Moreover, the voltage of the reverse power is converted according to theelectricity distribution system which causes a significant conversionloss in the process. Transmitting the power to another consumer alsocauses a transmission loss in the process as well. As such, it is moreenvironmental for the consumer to consume the generated power onlocation.

Furthermore, with the device proposed in PTL 2, the heat pump unit isoperated when the amount of generated power exceeds the amount of powerused. With this operation, the power consumption of the heat pump unitexceeds the surplus power, resulting in the purchase of an insufficientamount of power. As a result, hot water that has been heated withpurchased power in addition to surplus power is stored in a tank havinga limited hot water storage capacity, whereby a decrease in the reverseflow of power to the power grid cannot be efficiently realized.Moreover, the cost of power will increase due to the purchase of powerduring the daytime, when electricity rates are high.

In order to solve the above-described problem, the heat pump operationmethod according to an aspect of the present invention is a heat pumpoperation method for use in a system which includes a power generationdevice, an electric load which operates using power generated by thepower generation device, and a heat pump which generates heat using thepower generated by the power generation device. Specifically, the heatpump operation method includes: obtaining, on a per time unit basis,generated power which is an amount of the power generated by the powergeneration device, load power which is an amount of the power consumedby the electric load, and surplus power which is a difference betweenthe generated power and the load power; and controlling operation of theheat pump to cause the heat pump to generate heat using power adjustedto follow a per time unit increase or decrease in the surplus power. Inthe controlling, when an amount of change in the surplus power remainsgreater than a predetermined threshold value for a given period of timeextending back from a present time, an extent to which the powerconsumed by the heat pump follows the surplus power is reduced.

With this, by reducing the extent to which the power consumed by theheat pump follows the surplus power in a period of abrupt change insurplus power, heat pump load power is kept from abruptly fluctuating inexchange for permitting a small amount of reverse flow or purchase ofpower, resulting in stable operation of the heat pump.

Moreover, in the controlling, the extent to which the power consumed bythe heat pump follows the surplus power may be reduced when (i) theamount of change in the surplus power remains greater than thepredetermined threshold value for the given period of time extendingback from a present time and (ii) an amount of change in the load poweris greater than an amount of change in the generated power

With this, by also taking into consideration the cause of thefluctuations in surplus power when controlling the extent to which thepower consumption command value follows the surplus power, both theefficient consumption of surplus power while inhibiting the purchase ofpower and the stable operation of the heat pump can be achieved.

Moreover, in the controlling, the operation of the heat pump may becontrolled to approximate the power consumed by the heat pump to thesurplus power last obtained.

Moreover, in the controlling, the operation of the heat pump iscontrolled to cause the heat pump to consume an amount of power adjustedto follow the surplus power obtained on a per time unit basis when afirst condition is met, the first condition being that the surplus powerremains greater than a predetermined threshold value for the givenperiod of time extending back from a present time.

When conventional heat pumps are caused to operate using a reducedamount of power, the heat generation efficiently drastically decreases.Moreover, some time is required for the heat pump to go from a stoppedstate to a state of highly efficient operation. For that reason, asdescribed above, it is preferable that the power consumed by the heatpump is made to follow the surplus power only when (i) the amount ofsurplus power is great enough for the heat pump to operate in a highlyefficient manner, and (ii) it can be assured that the surplus power willbe continuously supplied until the operation of the heat pumpstabilizes.

Furthermore, in the obtaining, an amount of heat in a water storage tankwhich stores hot water heated by the heat generated by the heat pump maybe obtained on a per unit time basis. Then, in the controlling, theoperation of the heat pump may be controlled to cause the heat pump toconsume an amount of power adjusted to follow the surplus power obtainedon a per time unit basis when a second condition is met in addition tothe first condition, the second condition being that the amount of heatin the water storage tank last obtained is less than or equal to apredetermined upper limit.

Moreover, in the controlling, the operation of the heat pump may becontrolled to cause the heat pump to consume an amount of power adjustedto follow the surplus power obtained on a per time unit basis when athird condition is met in addition to the first condition and the secondcondition, the third condition being that the amount of heat in thewater storage tank last obtained is greater than a predetermined lowerlimit.

Even if the heat pump is caused to operate when the amount of heat inthe water storage tank exceeds the upper limit, generated heat cannot bestored. Moreover, there is a need to cause the heat pump to operaterapidly in order to store heat in the water storage tank when the amountof heat in the water storage tank is greater than or equal to the lowerlimit, regardless of the presence or absence of surplus power. It is forthis reason that it is preferable to cause the heat pump to consumepower in accordance with the surplus power only when the above-describedsecond and third conditions are met.

Moreover, the system may include the heat pump which generates heat, awater storage tank which stores hot water, and a heat exchanger whichheats the hot water stored in the water storage tank with the heatgenerated by the heat pump. In the controlling, an ambient temperaturewhich is a temperature surrounding the heat pump, an inlet watertemperature which is a temperature of the hot water flowing through theheat exchanger from the water storage tank, and a heated watertemperature which is a temperature of the hot water supplied to thewater storage tank from the heat exchanger may be obtained, controlparameters may be obtained, the control parameters being necessary for,when the temperature surrounding the heat pump is the ambienttemperature, (i) causing the heat pump to consume power adjusted tofollow the surplus power obtained on a per unit time basis, and (ii)causing the heat pump to increase the temperature of the hot water fromthe inlet water temperature to the heated water temperature, and theoperation of the heat pump may be controlled according to the obtainedcontrol parameters.

Moreover, in the controlling, the control parameters corresponding toinput information including the amount of power consumed by the heatpump, the ambient temperature, the inlet water temperature, and theheated water temperature, may be obtained by referring to a controltable holding the input information and the control parameterscorresponding to a combination of the input information.

Moreover, discrete values of the input information may be held in thecontrol table. In the controlling, when the combination of the obtainedinput information is not held in the control table, the controlparameters corresponding to the combination of the obtained inputinformation may be obtained by linear interpolation based on a pluralityof the control parameters held in the control table.

Moreover, in the controlling, when at least one of the first condition,the second condition, and the third condition is not met, the operationof the heat pump may be controlled to cause the heat pump to consume anamount of power comparable to a rated power of the heat pump.

A heat pump operation method according to another aspect of the presentinvention is a heat pump operation method for use in a system whichincludes a power generation device, an electric load which operatesusing power generated by the power generation device, and a heat pumpwhich generates heat using the power generated by the power generationdevice. Specifically, the heat pump operation method includes: obtaininggenerated power which is an amount of the power generated by the powergeneration device, load power which is an amount of the power consumedby the electric load, and surplus power which is a difference betweenthe generated power and the load power; and controlling operation of theheat pump by transmitting, to the heat pump, an amount of power to beconsumed by the heat pump for generating heat as a power consumptioncommand value. In the controlling, the power consumption command valueis calculated to follow the surplus power when the surplus power remainsgreater than or equal to a threshold value for a given period of time orlonger, when, furthermore, an amount of change in the surplus power isgreater than a threshold value, a power consumption command valueprevious to the calculated power consumption command value istransmitted to the heat pump as a second power consumption value, andwhen the amount of change in the surplus power is less than or equal tothe threshold value, the calculated power consumption command value istransmitted to the heat pump as the second power consumption commandvalue.

Moreover, when the power consumption command value is not obtained,control parameters may be calculated using a first control table, andwhen the power consumption command value is obtained, control parametersmay be calculated using a second control table which holds the powerconsumption command value.

The heat pump system according to an aspect of the present inventionincludes a power generation device, an electric load which operatesusing power generated by the power generation device, and a heat pumpwhich generates heat using the power generated by the power generationdevice. The heat pump system further includes: an information obtainingunit configured to obtain, on a per time unit basis, generated powerwhich is an amount of the power generated by the power generationdevice, load power which is an amount of the power consumed by theelectric load, and surplus power which is a difference between thegenerated power and the load power; and an operation control unitconfigured to cause the heat pump to generate heat using power adjustedto follow a per time unit increase or decrease in the surplus power. Theoperation control unit is further configured to, when an amount ofchange in the surplus power remains greater than a predeterminedthreshold value for a given period of time extending back from a presenttime, reduce an extent to which the power consumed by the heat pumpfollows the surplus power.

Moreover, the operation control unit may be configured to reduce theextent to which the power consumed by the heat pump follows the surpluspower when (i) the amount of change in the surplus power remains greaterthan the predetermined threshold value for the given period of timeextending back from a present time and (ii) an amount of change in theload power is greater than an amount of change in the generated power.

Moreover, the operation control unit may be configured to control theoperation of the heat pump to approximate the power consumed by the heatpump to the surplus power last obtained.

Moreover, the operation control unit may be configured to control theoperation of the heat pump to cause the heat pump to consume an amountof power adjusted to follow the surplus power obtained on a per timeunit basis when a first condition is met, the first condition being thatthe surplus power remains greater than a predetermined threshold valuefor a given period of time extending back from a present time.

Furthermore, the information obtaining unit may further be configured toobtain, on a per unit time basis, an amount of heat in a water storagetank which stores hot water heated by the heat generated by the heatpump, and the operation control unit may be configured to control theoperation of the heat pump to cause the heat pump to consume an amountof power adjusted to follow the surplus power obtained on a per timeunit basis when a second condition is met in addition to the firstcondition, the second condition being that the amount of heat in thewater storage tank last obtained is less than or equal to apredetermined upper limit.

Furthermore, the operation control unit may be configured to control theoperation of the heat pump to cause the heat pump to consume an amountof power adjusted to follow the surplus power obtained on a per timeunit basis when a third condition is met in addition to the firstcondition and the second condition, the third condition being that theamount of heat in the water storage tank last obtained is greater than apredetermined lower limit.

Moreover, the heat pump system may further include: the heat pump whichgenerates heat, a water storage tank which stores hot water, and a heatexchanger which heats the hot water stored in the water storage tankwith the heat generated by the heat pump. The operation control unit mayfurther be configured to: obtain an ambient temperature which is atemperature surrounding the heat pump, an inlet water temperature whichis a temperature of the hot water flowing through the heat exchangerfrom the water storage tank, and a heated water temperature which is atemperature of the hot water supplied to the water storage tank from theheat exchanger; obtain control parameters, the control parameters beingnecessary for, when the temperature surrounding the heat pump is theambient temperature, (i) causing the heat pump to consume power adjustedto follow the surplus power obtained on a per unit time basis, and (ii)causing the heat pump to increase the temperature of the hot water fromthe inlet water temperature to the heated water temperature; and controlthe operation of the heat pump according to the obtained controlparameters.

Moreover, the operation control unit may be configured to obtain thecontrol parameters corresponding to input information including theamount of power consumed by the heat pump, the ambient temperature, theinlet water temperature, and the heated water temperature, by referringto a control table holding the input information and the controlparameters corresponding to a combination of the input information.

Moreover, discrete values of the input information may be held in thecontrol table. The operation control unit may configured to, when thecombination of the obtained input information is not held in the controltable, obtain the control parameters which correspond to the combinationof the obtained input information by linear interpolation based on aplurality of the control parameters held in the control table.

Moreover, the operation control unit may be configured to control theoperation of the heat pump to cause the heat pump to consume an amountof power comparable to a rated power of the heat pump when at least oneof the first condition, the second condition, and the third condition isnot met.

Moreover, the heat pump system may include: a heat pump hot water supplydevice which includes the heat pump, a water storage tank which storeshot water, a heat exchanger which heats the hot water stored in thewater storage tank with the heat generated by the heat pump, and a heatpump control unit; and a heat pump (HP) control device which includesthe information obtaining unit and the operation control unit, and whichis structurally separate from the heat pump hot water supply device.

With the foregoing configuration, the HP control device can be caused tocontrol not only the heat pump hot water supply device, but otherelectronic devices as well. Moreover, when used in an environment inwhich control of power consumption is not necessary, it is suitable toinstall simply the heat pump hot water supply device.

A heat pump system according to another aspect of the present inventionincludes: a heat pump which generates heat using power generated by apower generation device; and a heat pump (HP) control device whichcontrols the heat pump. The HP control device includes: an informationobtaining unit configured to obtain an amount of the power generated bythe power generation device, an amount of load power, and a status of apower grid; and an operation control unit configured to calculate apower consumption command value using a value of surplus powercalculated based on the amount of power generated and the amount of loadpower. The operation control unit is further configured to: calculatethe power consumption command value to follow the surplus power when thesurplus power remains greater than or equal to a threshold value for agiven period of time or longer; when, furthermore, an amount of changein the surplus power is greater than a threshold value, transmit a powerconsumption command value previous to the calculated power consumptioncommand value to the heat pump as a second power consumption commandvalue; and when the amount of change in the surplus power is less thanor equal to the threshold value, transmit the calculated powerconsumption command value as the second power consumption command valueto the heat pump.

Moreover, The heat pump system may further include a power distributiondevice, wherein the power distribution device may transmit the amount ofpower generated and the amount of load power to the informationobtaining unit included in the HP control device.

Furthermore, the heat pump system further includes an HP hot watersupply device including the heat pump and an HP control unit. The HPcontrol unit may include a first control table for calculating operationparameters based on the power consumption command value and a secondcontrol table for calculating operation control parameters based onrated operation.

It is to be noted that general or specific embodiments may be realizedas a system, method, integrated circuit, computer program, storagemedia, or any elective combination thereof.

First Embodiment

Hereinafter, embodiments of present invention are described withreference to the drawings. It is to be noted that each of theembodiments described below shows a specific example of the presentinvention. The numerical values, shapes, materials, structural elements,the arrangement and connection of the structural elements, steps, theprocessing order of the steps etc. shown in the following exemplaryembodiments are mere examples, and therefore do not limit the presentinvention. Moreover, among the structural elements in the followingexemplary embodiments, structural elements not recited in any one of theindependent claims defining the most generic part of the inventiveconcept are described as arbitrary structural elements.

FIG. 1 is a flow chart outlining the processes of the heat pump hotwater supply system according to the first embodiment of the presentinvention.

As FIG. 1 shows, firstly, the heat pump hot water supply systemaccording to the first embodiment obtains surplus power (S101) which isthe amount of power generated by the photovoltaic device (PV-generatedpower) remaining after power to be consumed within the home has beenallotted for. Next, the heat pump hot water supply system determines,taking into account the surplus power, a given amount of power for theheat pump to consume and operate at (S102). The heat pump hot watersupply system then determines heat pump control parameters for theconsumption of the determined power, and causes the heat pump to operatein accordance with the control parameters (S103).

In this way, the heat pump operates such that it consumes an amount ofpower close to the surplus power, resulting in a decrease in the amountof reverse power sent to the power grid and a cost-effective mode ofoperation.

FIG. 2 is a block diagram explaining a heat pump hot water supply system2000 including the power generation device. As shown in FIG. 2, the heatpump hot water supply system 2000 according to the first embodimentincludes a heat pump hot water supply device 200, a power distributiondevice 204, a HP control device 209, and a photovoltaic device 210. Thepower distribution device 204 is connected to a first electric load 205and a power meter 206 via an energy supplier 207.

The energy supplier 207 (source of electric power) as shown in FIG. 2supplies power via a power grid to homes. The power grid is a networkthat provides a stable supply of power. The power meter 206 measures theamount of power supplied via the power grid that is consumed in a home.Moreover, the power meter 206 is configured to sell excess powergenerated by the photovoltaic device 210 that is not consumed in thehome to the power grid.

The house shown in FIG. 2 is equipped with the first electric load 205,the heat pump hot water supply device 200 (the second electric load),the HP control device 209, the photovoltaic device 210, and the powerdistribution device 204.

The heat pump hot water supply device 200 includes at least a heat pump(heat generation unit) 201, a heat exchanger 202, and a water storagetank (heat storage unit) 203. The heat generated by the heat pump 201 istemporarily stored in the water storage tank 203, and the hot waterinside the water storage tank 203 is radiated according to a user'srequest. That is, the heat pump hot water supply device 200 radiatesheat generated by the heat generation unit and stored in the heatstorage unit.

The photovoltaic device 210 is a device which converts energy from thesun into electric power. The photovoltaic device 210 converts energyfrom the sun into electric power and outputs the converted power(PV-generated power) to the power distribution device 204.

The power distribution device 204 obtains power from the photovoltaicdevice 210 and the energy supplier (commercial power source) 207, anddistributes the power to the heat pump hot water supply device 200 andthe first electric load 205 on demand. The heat pump hot water supplydevice 200 can operate off power from the photovoltaic device 210 aswell as off power bought from the energy supplier 207 (grid power).Moreover, the power distribution device 204 can measure the amount ofpower distributed to the heat pump hot water supply device 200 and thefirst electric load 205, that is, the amount of power consumed by theheat pump hot water supply device 200 and the first electric load 205.

The power distribution device 204 obtains the PV-generated power fromthe photovoltaic device 210. Moreover, the power distribution device 204measures load power, which is the amount of power consumed by the firstelectric load 205, and heat pump load power, which is the amount ofpower consumed by the heat pump hot water supply device 200. When thesum of the load power and the heat pump load power exceeds thePV-generated power, power purchased from the power grid is obtained viathe power meter 206. That is, the power distribution device 204 obtainspurchased power and PV-generated power, then supplies heat pump loadpower to the heat pump hot water supply device 200, and load power tothe first electric load 205. Moreover, when the PV-generated powerexceeds the sum of the load power and the heat pump load power, surpluspower can be transmitted as reverse power and sold to the energysupplier 207.

Moreover, the power distribution device 204 can inhibit the output ofPV-generated power corresponding to the surplus power when the voltageof the power grid is high and the reverse flow of surplus power is notpossible. More specifically, the power distribution device 204 stops thesupply (selling) of power to the energy supplier 207 via the power meter206 when the voltage of the power grid exceeds a threshold value (forexample, 107 V).

The power distribution device 204 also includes a converter and inverterwhich, when obtained power is transmitted as described above, convertsthe voltage and performs AC-DC and DC-AC conversion of the obtainedpower accordingly so the obtained power conforms to the transmittedpower. Moreover, the power distribution device 204 transmits the loadpower actually consumed by the first electric load 205 and thePV-generated power actually generated by the photovoltaic device 210 tothe HP control device 209 at regular time intervals.

The energy supplier 207 supplies purchased power at the demand of thepower distribution device 204 installed in the consumer's home.Additionally, when reverse power is input from the power distributiondevice 204, the energy supplier 207 transmits that power via the powergrid to other homes of consumers.

The first electric load 205 is an electric load inside the home of aconsumer, and refers to appliances such as televisions, airconditioners, refrigerators, washing machines, or lights which operateby using power supplied from the power distribution device 204.Furthermore, the sum total of the power used by these appliances isdefined herein as load power.

FIG. 3 is a block diagram detailing the heat pump hot water supplydevice 200. The heat pump hot water supply device 200 is mainlyconfigured from the heat pump 201, the heat exchanger 202, the waterstorage tank 203, the heat pump control unit 211, an ambient temperaturemeasuring unit 212, and an inlet water temperature measuring unit 213.The heat pump hot water supply device 200 operates using power receivedfrom the power distribution device 204.

Although not included in the Drawings, the heat pump 201 includes anevaporator which facilitates heat exchange between outside air and lowtemperature-low pressure liquid refrigerant to generate a lowtemperature-low pressure vaporized refrigerant, a motor-drivencompressor which compresses the low temperature-low pressure vaporizedrefrigerant into a high temperature-high pressure vaporized refrigerant,a condenser which facilitates heat exchange between the hightemperature-high pressure vaporized refrigerant and circulating water(thermal storage medium) to generate a low temperature-high pressureliquid refrigerant, an expansion valve which reduces the pressure of thelow temperature-high pressure vaporized refrigerant to generate a lowtemperature-low pressure liquid refrigerant, and a fan to accelerate theheat conversion between the refrigerant in the evaporator and theoutside air, for example.

The water storage tank 203 stores heat supplied by the hot water supplyload. The water storage tank 203 is consistently filled with water. Whenthe heat pump 201 begins to operate, water flows from the bottom of thewater storage tank 203 into the heat exchanger 202. The heat exchanger202 facilitates heat exchange between hot water (thermal storage medium)supplied from the heat pump 201 and water supplied from the waterstorage tank 203. The heated hot water then flows into the top of thewater storage tank 203. According to the first embodiment, the capacityof the water storage tank 203 is 400 L (unit: liters).

The heat pump control unit 211 controls the entire heat pump hot watersupply device 200 based on the power consumption command value(explained later) obtained from the HP control device 209 and based onthe state of the water storage tank 203. It is to be noted that thepower consumption command value is a value calculated by the HP controldevice 209 which indicates a given amount of power for the heat pump toconsume and operate at.

When the heat pump control unit 211 has not obtained the powerconsumption command value from the HP control device 209 (that is, isoperating in a normal mode of operation), the operation method of theheat pump 201 is determined based on the current cost of electricity andthe current state of the water storage tank 203. In other words, theheat pump heat pump 201 is caused to operate during the middle of thenight when the electricity rate is low until the water storage tank 203is full of hot water, and at all other times, when the amount of hotwater stored in the water storage tank 203 decreases to a given amount,the heat pump 201 is caused to operate such that hot water does not runout. Moreover, a heated water temperature, which is a temperature of thewater exiting the heat exchanger 202, is determined so that an amount ofhot water supply load supplied in one day can be stored.

Under the normal mode of operation, the heat pump control unit 211causes the heat pump 201 to operate at the rated power (1000 W, forexample) so that a certain amount of heat can be supplied from the heatpump 201 to the water storage tank 203. As shown in FIG. 4, a firstcontrol table configured to supply a certain amount of heat according tothe hardware characteristics of the heat pump 201 is stored in the heatpump control unit 211.

FIG. 4 shows an example of the first control table. When the inlet watertemperature, ambient temperature, and heated water temperature are inputas input information, the compressor frequency, expansion valveaperture, and pump flow rate of the water pump are output as outputinformation. These pieces of output information are the controlparameters for the heat pump 201 necessary to heat the water at theinlet water temperature to the heated water temperature in the ambienttemperature environment.

When the heat pump control unit 211 causes the heat pump 201 to operatein the normal mode of operation, the temperature of the water flowinginto the heat exchanger 202 from the water storage tank 203 (inlet watertemperature) is obtained from the inlet water temperature measuring unit213, and the ambient temperature surrounding the heat pump 201 isobtained from the ambient temperature measuring unit 212.

The ambient temperature measuring unit 212 is a thermistor whichmeasures the ambient temperature surrounding the heat pump 201. Theinlet water temperature measuring unit 213 is a thermistor whichmeasures the temperature of the water flowing into the heat exchanger202 from the water storage tank 203.

Next, the heat pump control unit 211 refers to the input information inthe first table which includes the obtained inlet water temperature, theobtained ambient temperature, and the heated water temperaturedetermined by the heat pump control unit 211 itself, performs linearinterpolation based on a plurality of columns including values close tothe value of the input information, then obtains the compressorfrequency, expansion valve aperture, and pump flow rate of the waterpump corresponding to the input information. The heat pump control unit211 then causes the heat pump 201 to operate according to the obtainedcompressor frequency, expansion valve aperture, and pump flow rate ofthe water pump, thereby causing the generation of a certain amount ofheat (causing the water at the inlet water temperature to be heated tothe heated water temperature) by causing the heat pump 201 to consumeits rated power.

On the other hand, when the heat pump control unit 211 obtains the powerconsumption command value from the HP control device 209 (that is, isoperating in a surplus-oriented mode of operation), the operation of theheat pump 201 is controlled so that the heat pump load power matches thepower consumption command value. As shown in FIG. 5, a second controltable designed to supply a certain amount of heat pump load poweraccording to the hardware characteristics of the heat pump 201 is storedin the heat pump control unit 211.

When the heat pump control unit 211 causes the heat pump 201 to operatein a surplus-oriented mode of operation, the inlet water temperature isobtained from the inlet water temperature measuring unit 213 and theambient temperature is obtained from the ambient temperature measuringunit 212, similar to under the normal mode of operation. Next, the heatpump control unit 211 refers to the obtained inlet water temperature,ambient temperature, power consumption command value, and heated watertemperature as input information in the second table, performs a linearinterpolation operation based on a plurality of columns including valuesclose to the value of the input information, then obtains the compressorfrequency, expansion valve aperture, and pump flow rate of the waterpump corresponding to the input information. The heat pump control unit211 then causes the heat pump 201 to operate according to the obtainedcompressor frequency, expansion valve aperture, and pump flow rate ofthe water pump (shown in FIG. 3), thereby causing the generation of acertain amount of heat (that is, causing the water at the inlet watertemperature to be heated to the heated water temperature) by causing theheat pump 201 to consume a given amount of power (the power consumptioncommand value).

It is to be noted that other than the addition of the power consumptioncommand value (unit: W) to the second control table shown in FIG. 5, thetable is the same as the first control table shown in FIG. 4. Moreover,the power consumption command value in the example shown in FIG. 5varies in 50 W increments, such as 500 W (lowest value), 550 W, and 600W. The control parameters are configured to cause the heat pump 201 toconsume an amount of power that is equivalent to this power consumptioncommand value.

That is, with the first control table, the heat pump 201 will operate atits rated power regardless of which control parameter is selected, whilewith the second control table, the heat pump 201 can be caused tooperate consuming a given amount of power (the power consumption commandvalue) depending on the control parameter selected.

As the flow of data in FIG. 6 shows, the HP control device 209calculates the power consumption command value, which is a given amountof power for the heat pump 201 to consume and operate at, taking intoaccount the load power and PV-generated power obtained from the powerdistribution device 204, the surplus power which is the differencebetween the PV-generated power and the load power, and the amount ofheat in the water storage tank obtained from the heat pump control unit211.

FIG. 7 is a block diagram detailing the HP control device 209. The HPcontrol device 209 includes an information obtaining unit 209 a, a powerinformation storage unit 209 b, and an operation control unit 209 c.

On a per unit time basis (every minute, for example), the informationobtaining unit 209 a obtains the amount of heat stored in the waterstorage tank 203, the amount of power generated by the photovoltaicdevice 210 (the PV-generated power), the load power consumed by thefirst electric load 205, and the surplus power which is the differencebetween the PV-generated power and the load power. It is to be notedthat the information obtaining unit 209 a according to the firstembodiment obtains the amount of heat stored in the water storage tankfrom the heat pump control unit 211, obtains the PV-generated power andthe load power from the power distribution device 204, and calculatesthe surplus power internally.

The power information storage unit 209 b stores information on thePV-generated power and the load power obtained by the informationobtaining unit 209 a each minute over the past 30 minutes, andinformation on the surplus power calculated by the information obtainingunit 209 a each minute over the past 30 minutes (surplus power record).An example of each type of information stored can be seen in FIG. 8. Itis to be noted that the surplus power is calculated by subtracting theload power from the PV-generated power. When the calculated value isnegative, the value is output as zero, and when the calculated value ispositive, the value is output as-is.

The surplus power record shown in FIG. 8 holds the load power (unit: W),the PV-generated power (unit: W), and the surplus power (unit: W) by theminute for the past 30 minutes. It is to be noted that the surplus poweris calculated in 10 W increments by subtracting the load power from thePV-generated power. However, when the load power exceeds thePV-generated power, the surplus power is shown as 0, such as the exampleshown in the 9 minutes before row. In this case, the power distributiondevice 204 compensates the insufficient portion of the energy with thepower purchased from the energy supplier 207.

Furthermore, FIG. 8 shows an example of the power consumption commandvalue calculated by the operation control unit 209 c at each time. Thepower consumption command value is set in 50 W increments, and thesurplus power is rounded down to the nearest 50 W increment. Forexample, in the example shown in the 10 minutes before row, the surpluspower (1010 W) is rounded down to make the power consumption commandvalue 1000 W.

Moreover, the lowest value of the power consumption command value is 500W. In other words, when the rounded off result is less than 500 W, thepower consumption command value is 0 W, as is the case in the 1 minutebefore row. This is because even if the heat pump 201 were caused tooperate at a low power consumption command value, the operationefficiency would be low.

Moreover, the power consumption command value is only calculated whenthe surplus power remains greater than a threshold value (the lowestconsumption power: 500 W for example) for a given period of time (theminimum surplus time: 15 minutes for example). In other words, thesurplus power in the 18 minute before row is above the threshold value,but in the 15 minutes up until that point in time, the surplus powerdecreased to or below the threshold value (not shown). For this reason,the power consumption command value in the 18 minutes before row is 0.The power consumption command value remains that value for one minuteafter it is determined. For example, the power consumption command valuein the 12 minutes before row is 650 W. This value stays the same for oneminute until the 11 minutes before time. When the time becomes 11minutes before, the value is 850 W and remains so for one minute untilthe 10 minutes before time.

The power information storage unit 209 b may be any means of storagecapable of recording data, such as dynamic random access memory (DRAM),synchronous dynamic random access memory (SDRAM), flash memory, orferrodielectric memory.

The operation control unit 209 c controls the operation of the heat pump201 so the power it consumes to generate heat increases and decreases inaccordance with the increases and decreases in the surplus power on aunit time basis. Specifically, the operation control unit 209 ccalculates and sends the power consumption command value, which is agiven amount of power for the heat pump 201 to consume and operate at,to the heat pump control unit 211 taking into account the surplus powerrecord and the amount of heat in the water storage tank. Detailsregarding the calculation method of the power consumption command valuewill be described later.

When the surplus power record and the amount of heat in the waterstorage tank each meet a predetermined condition, the operation controlunit 209 c calculates and sends the power consumption command value tothe heat pump control unit 211. Specifically, when (i) the surplus powerremains greater than a predetermined threshold value (the lowestconsumption power: 500 W) for a given period of time (the minimumsurplus time: 15 minutes) extending back from the present time (firstcondition), (ii) the current amount of heat in the water storage tank isless than or equal to a predetermined upper limit (a sufficient amountof heat) (second condition), and (iii) the current amount of heat in thewater storage tank is greater than a predetermined lower limit (aninsufficient amount of heat) (third condition), the operation controlunit 209 c calculates and sends the power consumption command value tothe heat pump control unit 211.

The lowest consumption power is the lowest amount of power at which theheat pump 201 can maintain or exceed a certain level of efficiency onaccount of the heat pump cycle of the heat pump 201 which depends on therefrigerant used. The minimum surplus time is a preset amount of timeduring which it can be assured that surplus power will be suppliedstably. Moreover, a sufficient amount of heat refers to a maximum amountof heat that can be stored in the water storage tank 203 (for example25000 kcal), while an insufficient amount of heat refers to a bareminimum amount of heat that should be stored in the water storage tank203 to keep hot water from running out (for example 5000 kcal), similarto in the normal mode of operation as previously described. In otherwords, when the amount of heat inside the water storage tank 203 dropsbelow the insufficient amount of heat, the heat pump 201 starts thenormal mode of operation instead of the surplus-oriented mode ofoperation.

That is, when (i) the heat pump 201 can remain at or above a certainlevel of efficiency and operate continuously until the level ofefficiency stabilizes after starting to operate while only consumingsurplus power (first condition), (ii) the heat pump 201 can still storeheat in the water storage tank 203 (second condition), and (iii) theamount of heat in the water storage tank 203 is sufficient enough thathot water will not run out (third condition), the operation control unit209 c calculates and sends the power consumption command value to theheat pump control unit 211.

The power consumption command value is sent only when these threeconditions are met, that is to say, when the heat generation efficiencyof the heat pump 201 can be maintained, heat can additionally be storedin the water storage tank 203, and the water storage tank 203 will notrun out of hot water. When sent, the heat pump 201 is caused to operateby consuming power in accordance with the surplus power, as previouslydescribed.

Hereinafter, an exemplary operation of the heat pump hot water supplysystem 2000 according to the first embodiment is described. Thedescription will be given on the premise that the present time is12:00:00, and the heat pump hot water supply system 2000 has beencontinuously operating for 30 minutes or more. Moreover, the heatedwater temperature of the heat pump 201 is 70 degrees Celsius, asdetermined by the heat pump control unit 211.

FIG. 9 is a flowchart of operation processes performed on a per minutebasis by the HP control device 209 and the heat pump control unit 211.

First, the HP control device 209 calculates the power consumptioncommand value (S1101). FIG. 10 is a flowchart of processes performed bythe HP control device 209 related to the calculation of the powerconsumption command value (S1101).

First, the information obtaining unit 209 a compares the previousprocessing time with the current processing time, and determines whetherone minute has passed since the previous processing time (S1201). Aspreviously described, since the present time is 12:00:00, it isdetermined that the minute value has changed since the previousprocessing time (yes in S1201).

When yes in S1201, the information obtaining unit 209 a updates thesurplus power record stored in the power information storage unit 209 b(S1202). The information obtaining unit 209 a obtains the average loadpower over the past minute and the average PV-generated power over thepast minute from the power distribution device 204. Moreover, theinformation obtaining unit 209 a subtracts the load power from thePV-generated power. The information obtaining unit 209 a sets thesurplus power to zero if the value is negative, and sets the surpluspower to the calculated value if the value is positive. The informationobtaining unit 209 a then discards the value from 30 minutes ago (theoldest value) from the surplus power record stored in the powerinformation storage unit 209 b, and stores the most recent PV-generatedpower, load power, and surplus power as values for the previous minute.

On the other hand, when it is determined that the minute value has notchanged since the previous processing time (no in S1201), the surpluspower record is not updated.

Next, the information obtaining unit 209 a obtains other informationused in the calculation of the power consumption command value (S1203).Specifically, the information obtaining unit 209 a obtains the surpluspower record and the last obtained surplus power from the powerinformation storage unit 209 b, and obtains the amount of heat in thewater storage tank from the heat pump control unit 211. The informationobtaining unit 209 a then transmits the obtained information to theoperation control unit 209 c.

The operation control unit 209 c determines whether or not the surpluspower record meets the first condition (S1204). The first conditionaccording to the first embodiment is that the surplus power remainsgreater than the lowest consumption power for the minimum surplus timeor longer. Moreover, according to the first embodiment, the lowestconsumption power is 500 W and the minimum surplus time is 15 minutes.For example, when the surplus power values between 1 minute before and15 minutes before in the current surplus power record all exceed 500 W,it is determined that the surplus power record meets the first condition(yes in S1204).

Next, the operation control unit 209 c determines whether or not theamount of heat in the water storage tank meets the second and thirdconditions (S1205). The second condition according to the firstembodiment is that the previous amount of heat in the water storage tankis less than or equal to the sufficient amount of heat. The thirdcondition according to the first embodiment is that the previous amountof heat in the water storage tank exceeds the insufficient amount ofheat. Moreover, according to the first embodiment, the sufficient amountof heat is 25,000 kcal, and the insufficient amount of heat is 5,000kcal. If the previous amount of heat in the water storage tank is 10,000kcal, for example, it is determined that the amount of heat in the waterstorage tank meets the second and third conditions (yes in S1205).

On the other hand, when the surplus power record does not meet the firstcondition (no in S1204), or when the amount of heat in the water storagetank does not meet the second and third conditions (no in S1205), theoperation control unit 209 c ends the processing without calculating thepower consumption command value.

When the first through third conditions are met (yes in S1205), theoperation control unit 209 c determines whether the amount of change insurplus power obtained over a given period of time extending back fromthe present time is greater than a predetermined threshold value(S1206).

It is to be noted that, the “given period of time” in S1206 is muchshorter than the “minimum surplus time” according to the firstcondition. The given period of time is, for example, approximately from30 seconds to two minutes. Moreover, the “threshold value” in S1206 is avalue determined in advance based on a per unit time amount of change inpower that the heat pump 201 is capable of following. The thresholdvalue is, for example, approximately from 500 W to 1500 W. Moreover, the“given period of time” and the “threshold value” described above arecorrelated, and in general, the smaller the “given period of time” is,the smaller the “threshold value” is. For example, the threshold valuefor a given time period of one minute can be set to 1000 W. Furthermore,the “given period of time” and the “threshold value” are not limited tofixed values, but may be updated based on previous shifts in surpluspower, for example.

When the amount of change in surplus power obtained over a given periodof time is not greater than a predetermined threshold value (no inS1206), the operation control unit 209 c calculates the powerconsumption command value based on the surplus power, and transmits thepower consumption command value to the heat pump control unit 211(S1208). Specifically, the operation control unit 209 c sets the powerconsumption command value to the previous (most recent) surplus power.Here, the previous surplus power is the surplus power (W) numericalvalue shown in the one minute before row in FIG. 8. In other words, theprevious surplus power is the most recent surplus power shown in thetable in FIG. 8. The power consumption command value based on thisprevious (most recent) surplus power value remains that value for oneminute.

Moreover, it is not necessary to make the power consumption commandvalue the exact surplus power, as-is. The power consumption commandvalue may be made a value that is slightly lower than the surplus power.For example, if the previous surplus power is 650 W, the powerconsumption command value may be made 630 W. However, it is not suitablefor the power consumption command value to be set to a value that islarger than the surplus power.

Conversely, when the amount of change in surplus power obtained over agiven period of time is greater than a predetermined threshold value(yes in S1206), the operation control unit 209 c does not make thepreviously obtained surplus power the power consumption command value,but rather transmits the last calculated power consumption command valueto the heat pump control unit 211 (S1209). In other words, in this case,the power consumption command value temporarily stops the amount ofpower consumed by the heat pump 201 from following the increases anddecreases in surplus power (that is, reduces the extent to which thepower consumed by the heat pump follows the surplus power). Next,calculation of the last calculated power consumption command value willbe discussed in further detail. Suppose that up until the two minutesbefore row, the amount of fluctuation in the surplus power is within thethreshold, but exceeds the threshold value at the one minute before row.In this case, the power consumption command value from the two minutesbefore row, which up until this point has been within the threshold, iscontinued to be used as the power consumption command value instead ofthe surplus power in the one minute before row. In other words, in orderto keep the power consumption command value from following the surpluspower, a previously obtained power consumption command value from whenthe amount of fluctuation is within the threshold is adopted as to bethe power consumption command value, not the most recent surplus power.

Next, returning to FIG. 9, the heat pump control unit 211 performs theprocesses related to the calculation of the control parameters for theheat pump 201 using the power consumption command value obtained fromthe HP control device 209 (S1102). FIG. 11 is a flowchart of theprocesses related to the calculation of the control parameters for theheat pump 201 (S1102) performed by the heat pump control unit 211.

First, the heat pump control unit 211 determines whether a new powerconsumption command value has been obtained from the HP control device209 (S1301).

When “yes” in S1301, the heat pump control unit 211 obtains inputinformation needed to calculate the control parameters (S1302). The heatpump control unit 211 obtains, from the inlet water temperaturemeasuring unit 213, the inlet water temperature of the water supplied tothe heat exchanger 202 from the water storage tank 203, and obtains theambient temperature surrounding the heat pump 201 from the ambienttemperature measuring unit 212. It is to be noted that the heated watertemperature is held in the heat pump control unit 211 in advance, andthe power consumption command value has already been obtained from theHP control device 209.

Next, the heat pump control unit 211 refers to the second control tableand obtains output information corresponding to the inlet watertemperature, ambient temperature, heated water temperature, and powerconsumption command value obtained as input information (S1303). Anexample of the input information is shown in FIG. 12A, and an example ofthe second control table is shown in FIG. 12B. In this example, as theinput information, the power consumption command value obtained is 1000W, the inlet water temperature obtained is 13 decrees Celsius, theambient temperature obtained is 11 degrees Celsius, and the heated watertemperature obtained is 70 degrees Celsius. Upon referring to the secondcontrol table, the power consumption command value and the heated watertemperature are consistent throughout the input information, but theinlet water temperature and the ambient temperature are not.

The values set in the second control table are discrete values.Therefore, when there is no set of values in the second control tablethat do not exactly match the combination of the input information, theheat pump control unit 211 calculates the control parameters usinglinear interpolation (S1304). The heat pump control unit 211 uses inputinformation and output information between columns in the second controltable to obtain, by linear interpolation, output information whichcorresponds to the input information.

FIG. 13A and FIG. 13B show an example of a result of the linearinterpolation using the input information shown in FIG. 12A and thesecond control table shown in FIG. 12B.

In the following example, a linear interpolation is applied with respectto the ambient temperature as the first linear interpolation. Theresults shown in FIG. 13A are calculated by applying a linearinterpolation to the output information between the columns in whichonly the ambient temperatures in the second control table shown in FIG.12B are different using the ambient temperature (11 degrees Celsius). Inother words, the first column in FIG. 13A is the result of the linearinterpolation of the first and second columns in FIG. 12B, and thesecond column in FIG. 13A is the result of the linear interpolation ofthe third and fourth columns in FIG. 12B.

Furthermore, a linear interpolation is applied a second time withrespect to the inlet water temperature using the result of the firstlinear interpolation shown in FIG. 13A. The results shown in FIG. 13Bare calculated by applying a linear interpolation to the outputinformation between the columns in which only the inlet watertemperatures in FIG. 13A are different using the inlet water temperature(13 degrees Celsius). As a result, output information which correspondsto the input information shown in FIG. 12A is obtained. In other words,when the operation of the heat pump 201 is controlled using thecalculated output information (S1309), the heat pump 201 consumes anamount of power that is close to the power consumption command value.

On the other hand, when a new power consumption command value is notobtained (no in S1301), the heat pump control unit 211 determineswhether to cause the heat pump 201 to operate in the normal mode ofoperation (S1305). In other words, the heat pump control unit 211, aspreviously described, determines whether to cause the heat pump 201 tooperate in the normal mode of operation while taking into considerationthe current cost of electricity and the current amount of stored hotwater in the water storage tank 203. Specifically, under the normal modeof operation, the heat pump heat pump 201 is caused to operate duringthe middle of the night when the electricity rate is low until the waterstorage tank 203 is full of hot water, and at all other times, when theamount of hot water stored in the water storage tank 203 decreases to agiven amount, the heat pump 201 is caused to operate such that hot waterdoes not run out.

When “yes” in S1305, the heat pump control unit 211 obtains inputinformation necessary for calculating the control parameters (S1306),refers to the first control table (S1307), and applies a linearinterpolation when necessary (S1308), whereby the control parameters arecalculated. It is to be noted that the processes in S1306 to S1308 arethe same as S1302 to S1304 except for the fact that the powerconsumption command value is not included in the input information andthat the first control table is being used. As such, explanation thereofwill be omitted.

When the operation of the heat pump 201 is controlled using thecalculated output information (S1309), the rated power is consumed bythe heat pump 201 and a certain amount of heat is supplied.

However, when “no” in S1305, the heat pump control unit 211 ends theprocessing without calculating the control parameters for the heat pump201 due to non-operation of the heat pump 201.

The heat pump control unit 211 controls the operation of the heat pump201 using the control parameters calculated in the above processes. Thepower consumed by the heat pump 201 operating according to the controlparameters calculated in especially S1302 to S1304 is a value that isthe same as or close to the power consumption command value calculatedby the HP control device 209. Since the power consumption command valueis updated on a per time unit basis, the power consumed by the heat pump201 (the heat pump load power) increases and decreases with the powerconsumption command values on a per time unit basis.

However, when the variation in power consumption command values is largeand the heat pump load power cannot keep up with the variations in thepower consumption command values, there are cases in which the heat pumpload power and the power consumption command value momentarily deviatefrom each other. That is, the heat pump control unit 211 controls theoperation of the heat pump 201 to bring the heat pump load power closerto the previously obtained power consumption command value (surpluspower).

Here, the relationship between the change in surplus power and thecalculated power consumption command value will be explained withreference to FIG. 14.

First, when the amount of change in surplus power is less than or equalto the threshold value (no in S1206 shown in FIG. 10), the powerconsumption command value calculated in S1208 in FIG. 10 is a value thatis the same as or very close to the previous surplus power. In otherwords, in FIG. 14, the power consumption command values in the timeperiods having a white background are made to closely follow theincreases and decreases in the surplus power (the extent to which thepower consumed follows the surplus power is high). As a result, themajority of the surplus power is consumed by the heat pump 201, and theamount of power sent in reverse through the power grid is greatlyreduced.

On the other hand, when the amount of change in surplus power is greaterthan the threshold value (yes in S1206 shown in FIG. 10), the powerconsumption command value calculated in S1209 in FIG. 10 is not the lastcalculated power consumption command value, but is a value equal to apower consumption command value calculated previous to the lastcalculated power consumption command value. In other words, in FIG. 14,the power consumption command values in the time periods having a shadedbackground are values which temporarily deviate from the surplus power,reducing the extent to which the power consumed follows the surpluspower. As a result, reverse power is generated when the surplus powerexceeds the power consumption command value, and power is purchased whenthe power consumption command value exceeds the surplus power.

Here, an abrupt change in surplus power occurs when, for example,operation of a hair dryer, microwave oven, or some other first electricload 205 is started or stopped. This abrupt change in surplus power, asis shown in FIG. 14, tends to peak and return to its original value in arelatively short span of time. In other words, a rapid increase and arapid decrease in surplus power tend to occur as a set within a shortperiod of time.

The amount of change in consumption power that the heat pump 201 isgenerally capable of following is, at most, approximately 200 W to 300 Wper minute. In other words, when the amount of change between powerconsumption command values exceeds this amount, the heat pump 201 cannotactually consume an amount of power which keeps up with the powerconsumption command value, leading to a temporary deviation in the heatpump load power and the power consumption command value.

More specifically, even if a power consumption command value wascalculated to follow the abrupt increase in surplus power shown in theperiod (1) in FIG. 14, a lag would occur as the heat pump load powercould not follow such a power consumption command value. Consequently,the reverse flow of power would occur. Next, after the abrupt increasein surplus power shortly comes to an end, the heat pump load power wouldbe in the process of gradually rising at the time the rapid decrease insurplus power shown in the period (2) in FIG. 14 begins. Even if thepower consumption command value were made to follow this rapid decrease,the heat pump load power would not be able to keep up. Consequently, thepurchase of power would occur.

In this way, even if the heat pump load power is forcedly made to followthe abrupt changes in surplus power, in the end, the heat pump loadpower will not be able to keep up, resulting in the reverse flow ofpower as well as the purchase of power. For this reason, the HP controldevice 209 temporarily makes the power consumption command value stopfollowing the surplus power during a period of abrupt change in surpluspower. In other words, a substantially constant power consumptioncommand value is maintained by adopting a value equal to a powerconsumption command value previous to the most recent power consumptioncommand value instead of the most recent surplus power. With the presentinvention, abrupt fluctuations in heat pump load power can be preventedin exchange for permitting a small amount of power to flow in reverse orthe purchase of power, resulting in stable operation of the heat pump201.

Hereinafter, an advantage of the heat pump hot water supply system 2000including the power generation device according to the first embodimentof the present invention is described.

The heat pump control unit 211 stores the first control table used inthe normal mode of operation, and the second control table used when theheat pump load power is caused to follow the power consumption commandvalue (surplus power). The second control table is generated based onactual tests conducted beforehand to make the heat pump load power comeclose to the power consumption command value and is stored in the heatpump control unit 211. As a result, the heat pump load power follows thevariation in the power consumption command value as previouslydescribed, and a cost-effective mode of operation can be achieved.

With the present invention, a small amount of reverse flow or purchaseof power is permitted in exchange for the prevention of abruptfluctuation in heat pump load power, which is achieved by temporarilystopping the power consumption command values from following the surpluspower in a period of rapid change in surplus power, resulting in stableoperation of the heat pump 201.

Moreover, satisfaction of the condition (the first condition) in whichthe surplus power remains greater than the lowest consumption power forthe minimum surplus time or longer counting back from the present time,is one condition for the output of the power consumption command valueby the HP control device 209. It is preferable that the lowestconsumption power be set to the lowest amount of power at which the heatpump 201 can maintain a given level of efficiency or above on account ofthe heat pump cycle of the heat pump 201 which depends on therefrigerant used. With this, the worsening of the cycle characteristicand the low efficiency operation of the heat pump 201 due to anextremely low power consumption command value being calculated ceases.

Moreover, satisfaction of the first condition means that the surpluspower has been generating stably for a given period of time (minimumsurplus time) counting back from the present time, as well as that it ishighly likely that a given amount of surplus power or more is generated.There is a problem with the heat pump 201 in that some time is requiredfor the heat pump to reach rated operation after being turned on, andduring that time, the operation efficiency of the heat pump 201 is low.In other words, when the supply of surplus power is unstable, the heatpump 201 stops operating shortly after being turned on, resulting inlow-efficient operation. For that reason, it is preferable that theminimum surplus time in the first condition be set to an amount of timerequired for the heat pump 201 to reach rated operation after beingturned on. Consequently, the heat pump 201 will cease to operate at alow level of efficiency.

With the configuration described in the first embodiment, the heat pumphot water supply system 2000 including the photovoltaic device 210 canachieve a decrease in the amount of reverse power transmitted to thepower grid as well as a cost-effective mode of operation.

Hereinbefore the heat pump hot water supply system 2000 according to thefirst embodiment was described, but the following embodiment is alsoacceptable.

The photovoltaic device 210 was described as an example of a powergeneration device, but other power generation devices such as thosewhich use wind power or fuel cells may be used.

Moreover, the HP control device 209 including the function of thegateway is located external to the heat pump hot water supply device200, but may be located internally in the heat pump hot water supplydevice 200 or internally in the power distribution device 204. Moreover,the operation control function of the HP control device 209 may beprovided in the heat pump hot water supply device 200 or the powerdistribution device 204.

Moreover, the HP control device 209 and the heat pump control unit 211implement the operation control on a per minute basis, but may also beimplemented on a per one-hundredth of a second or on a per second basis.

Furthermore, in FIG. 10, it is shown that the processing proceeds toS1206 only when the first through third conditions are met, but theprocessing is not limited thereto. In other words, the determination ofwhether to calculate the power consumption command value can be madewith a different condition while omitting a part of the first throughthird embodiments. For example, in the heat pump hot water supply device200 installed in a home, when the amount of heat inside the waterstorage tank 203 is regularly within range with respect to thesufficient amount of heat and the insufficient amount of heat, theprocessing load of the operation control unit 209 c can be reduced byomitting the processes of determining the second and third conditions.In this case, in FIG. 10, the processing would flow from yes in S1204 toS1206, skipping over S1205.

Second Embodiment

Next, operation of the heat pump hot water supply system according tothe second embodiment of the present invention will be explained withreference to FIG. 15 through FIG. 17. The explanation will thereforefocus on the points inherent in the second embodiment, and detailsregarding common points with the first embodiment will be omitted.

FIG. 15 is a flow chart showing a different embodiment of that of FIG.10. The flow chart shown in FIG. 15 is the same as the flow chart shownin FIG. 10 with the exception that S1207 is added after S1206. In otherwords, when the amount of change in surplus power obtained over a givenperiod of time is greater than a predetermined threshold value (yes inS1206), the operation control unit 209 c according to the secondembodiment compares the amount of change in load power in a given periodof time extending back from the present time with the amount of changein PV-generated power in a period corresponding to the given period(S1207).

When the amount of change in load power is greater than the amount ofchange in PV-generated power (yes in S1207), the operation control unit209 c does not make the most recent surplus power the power consumptioncommand value, but rather transmits the previous power consumptioncommand value to the heat pump control unit 211 (S1209). Conversely,when the amount of change in load power is less than or equal to theamount of change in PV-generated power (no in S1207), the operationcontrol unit 209 c a power consumption command value which follows themost recent surplus power to the heat pump control unit 211 (S1208).

Next, an advantage of the second embodiment is described with referenceto FIG. 16 and FIG. 17. FIG. 16 and FIG. 17 show the relationshipbetween the surplus power, the power consumption command values, thePV-generated power, and the load power. FIG. 16 is a graph forillustrating the result when S1207 is determined as “yes” in FIG. 15,and FIG. 17 is a graph for illustrating the result when S1207 isdetermined as “no” in FIG. 15.

Firstly, the surplus power is a difference between the PV-generatedpower and the load power. This means that an abrupt fluctuation insurplus power is a result of a rapid fluctuation in PV-generated poweror load power More specifically, an abrupt fluctuation in surplus powerresults from situations in which, for example, the PV-generated powerstays substantially constant and only the load power abruptlyfluctuates, the load power stays substantially constant and only thePV-generated power abruptly fluctuates, or the PV-generated power andthe load power abruptly fluctuate in mutually different directions.

Here, the main cause for the fluctuation in load power is the startingand stopping of operation of the first electric load 205. For thisreason, fluctuation in load power is generally abrupt and ends rapidly,as can be seen in FIG. 16. Thus, even if the power consumption commandvalue is made to follow to the fluctuations in surplus power when theamount of change in load power is relatively large (yes in S1207 in FIG.15), the heat pump load power cannot keep up, similar to as is explainedin the first embodiment. In this situation, instead of a powerconsumption command value calculated based on the most recent surpluspower value, it is preferable that a previous power consumption commandvalue be transmitted to the heat pump control unit 211 (it is preferredthat the power consumption command value does not follow the surpluspower) (S1209 in FIG. 15).

On the other hand, the main cause for the fluctuation in PV-generatedpower is changes in weather or changes in sunrise and sundown times, forexample. For this reason, it is likely that a fluctuation in thePV-generated power will continue for a relatively long period of time.Thus, compared to load power, fluctuation in PV-generated power isgenerally gradual and long lasting, as can be seen in FIG. 17. In thissituation, it is preferable that a power consumption command valuecalculated based on the most recent surplus power value be transmittedto the heat pump control unit 211 (it is preferred that the powerconsumption command value follow the surplus power).

With this, by also taking into consideration the cause of thefluctuations in surplus power when controlling the extent to which thepower consumption command value follows the surplus power, both theefficient consumption of surplus power while inhibiting the purchase ofpower and the stable operation of the heat pump 201 can be achieved.

In the second embodiment as well, it is shown in FIG. 15 that theprocessing proceeds to S1206 only when the first through thirdconditions are met, but the processing is not limited thereto. In otherwords, the determination of whether to calculate the power consumptioncommand value can be made with a different condition while omitting apart of the first through third conditions. For example, in the heatpump hot water supply device 200 installed in a home, when the amount ofheat inside the water storage tank 203 is regularly within range withrespect to the sufficient amount of heat and the insufficient amount ofheat, the processing load of the operation control unit 209 c can bereduced by omitting the processes of determining the second and thirdconditions. In this case, in FIG. 15, the processing would flow from yesin S1204 to S1206, skipping over S1205.

It should be noted that although the present invention was describedbased on the previous embodiments, the present invention is not limitedto these embodiments. The following examples are also intended to beincluded within the scope of the present invention.

Each of the preceding devices is, specifically, a computer systemconfigured from a microprocessor, ROM, RAM, a hard disk unit, a displayunit, a keyboard, and a mouse, for example. A computer program is storedin the RAM or the hard disk unit. Each of the devices achieves itsfunction as a result of the microprocessor operating according to thecomputer program. Here, the computer program is configured of aplurality of pieced together instruction codes indicating a command tothe computer in order to achieve a given function.

A portion or all of the components of each of the preceding devices maybe configured from one system LSI (Large Scale Integration). A systemLSI is a super-multifunction LSI manufactured with a plurality ofcomponents integrated on a single chip, and is specifically a computersystem configured of a microprocessor, ROM, and RAM, for example. Acomputer program is stored in the RAM. The system LSI achieves itsfunction as a result of the microprocessor operating according to thecomputer program.

A portion or all of the components of each of the preceding devices mayeach be configured from a detachable IC card or a stand-alone module.The IC card and the module are computer systems configured from amicroprocessor, ROM, and RAM, for example. The IC card and the modulemay include the super-multifunction LSI described above. The IC card andthe module achieve their function as a result of the microprocessoroperating according to a computer program. The IC card and the modulemay be tamperproof.

The present invention may be a method shown above. Moreover, the presentinvention may also be a computer program realizing these methods with acomputer, or a digital signal of the computer program.

Moreover, the present invention may also be realized as the computerprogram or the digital signal stored on storage media readable by acomputer, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM,DVD-RAM, DVD-RAM, BD (Blu-ray Disc), or a semiconductor memory. Thepresent invention may also be the digital signal stored on the abovementioned storage media.

Moreover, the present invention may also be realized by transmitting thecomputer program or the digital signal, for example, via an electriccommunication line, a wireless or wired line, a network such as theInternet, or data broadcasting.

Moreover, the present invention may be a computer system includingmemory storing the computer program and a microprocessor operatingaccording to the computer program.

Moreover, the computer program or the digital signal may be implementedby an independent computer system by being stored on the storage mediaand transmitted, or sent via the network, for example.

The preceding embodiments and the preceding transformation examples maybe individually combined.

Hereinbefore, the embodiments of the present invention were describedwith reference to the drawings, but the present invention is not limitedto the embodiments depicted in the drawings. It is acceptable to addvariations to or modify the embodiments depicted in the drawings withinthe scope of the invention or an equal scope.

INDUSTRIAL APPLICABILITY

The HP control device according to the present invention is useful as adevice which contributes to the reduction of energy costs and to thestabilization of the power grid when a hot water supply system or a hotwater supply and heating system, for example, is in operation.

REFERENCE SIGNS LIST

-   200 heat pump hot water supply device-   201 heat pump-   202 heat exchanger-   203 water storage tank-   204, 304 power distribution device-   205 first electric load-   206 power meter-   207 energy supplier-   209, 309 HP control device-   209 a, 309 a information obtaining unit-   209 b, 309 b power information storage unit-   209 c, 309 c operation control unit-   210 photovoltaic device-   211 heat pump control unit-   212 ambient temperature measuring unit-   213 inlet water temperature measuring unit-   2000, 3000 heat pump hot water supply system

The invention claimed is:
 1. A heat pump operation method for use in asystem which includes a power generation device, an electric load whichoperates using power generated by the power generation device, and aheat pump which generates heat using the power generated by the powergeneration device, the method comprising: obtaining, at predeterminedtime intervals, generated power, which is an amount of the powergenerated by the power generation device, load power, which is an amountof power consumed by the electric load, and surplus power, which is adifference between the generated power and the load power; andcontrolling, at the predetermined time intervals, an operation of theheat pump to cause the heat pump to generate heat using power determinedbased on the surplus power, wherein, in the controlling, when thesurplus power remains greater than or equal to a predetermined amount ofpower for a first period of time or longer, which is a given priorperiod of time, measured from a present time, and an amount of change inthe surplus power in a second period of time, which is a given priorperiod of time, measured from the present time, and shorter than thefirst period of time, is equal to or smaller than a predeterminedthreshold value, the operation of the heat pump is controlled togenerate heat using power that follows an increase or decrease in thesurplus power, and when the surplus power remains greater than or equalto the predetermined amount of power for the first period of time orlonger, and the amount of change in the surplus power in the secondperiod of time is greater than the predetermined threshold value, theoperation of the heat pump is controlled to generate heat using powerthat does not follow the increase or decrease in the surplus power. 2.The heat pump operation method according to claim 1, wherein, in thecontrolling, the operation of the heat pump is controlled to generateheat using power that does not follow the increase or decrease in thesurplus power, when the amount of change in the surplus power in thesecond period of time is greater than the predetermined threshold value,and an amount of change in the load power is greater than an amount ofchange in the generated power.
 3. The heat pump operation methodaccording to claim 1, wherein, in the controlling, the operation of theheat pump is controlled to generate heat using the power approximatelycorresponding to the surplus power last obtained.
 4. The heat pumpoperation method according to claim 1, wherein, in the controlling, theoperation of the heat pump is controlled to cause the heat pump toconsume an amount of power adjusted to follow the surplus powerobtained, when a first condition is met, the first condition being thatthe surplus power remains greater than the predetermined amount of powerfor the first period of time.
 5. The heat pump operation methodaccording to claim 4, wherein, in the obtaining, an amount of heat in awater storage tank which stores hot water heated by the heat generatedby the heat pump is obtained at the predetermined time intervals, and inthe controlling, the operation of the heat pump is controlled to causethe heat pump to consume the amount of power adjusted to follow thesurplus power obtained at the predetermined time intervals, when asecond condition is met, in addition to the first condition, the secondcondition being that the amount of heat in the water storage tank lastobtained is less than or equal to a predetermined upper limit.
 6. Theheat pump operation method according to claim 5, wherein, in thecontrolling, the operation of the heat pump is controlled to cause theheat pump to consume the amount of power adjusted to follow the surpluspower obtained at the predetermined time intervals, when a thirdcondition is met, in addition to the first condition and the secondcondition, the third condition being that the amount of heat in thewater storage tank last obtained is greater than a predetermined lowerlimit.
 7. The heat pump operation method according to claim 1, whereinthe system includes the heat pump which generates heat, a water storagetank which stores hot water, and a heat exchanger which heats the hotwater stored in the water storage tank with the heat generated by theheat pump, and in the controlling: an ambient temperature, which is atemperature surrounding the heat pump, an inlet water temperature, whichis a temperature of the hot water flowing through the heat exchangerfrom the water storage tank, and a heated water temperature, which is atemperature of the hot water supplied to the water storage tank from theheat exchanger are obtained; control parameters are obtained, thecontrol parameters (i) causing the heat pump to consume an amount ofpower adjusted to follow the surplus power obtained at the predeterminedtime intervals, and (ii) causing the heat pump to increase thetemperature of the hot water from the inlet water temperature to theheated water temperature; and the operation of the heat pump iscontrolled according to the obtained control parameters.
 8. The heatpump operation method according to claim 7, wherein in the controlling,the control parameters corresponding to input information including theamount of power consumed by the heat pump, the ambient temperature, theinlet water temperature, and the heated water temperature, are obtainedby referring to a control table holding the input information and thecontrol parameters corresponding to a combination of the inputinformation.
 9. The heat pump operation method according to claim 8,wherein discrete values of the input information are held in the controltable, and in the controlling, when the combination of the obtainedinput information is not held in the control table, the controlparameters corresponding to the combination of the obtained inputinformation are obtained by linear interpolation based on a plurality ofthe control parameters held in the control table.
 10. The heat pumpoperation method according to claim 6, wherein in the controlling, whenat least one of the first condition, the second condition, and the thirdcondition is not met, the operation of the heat pump is controlled tocause the heat pump to consume an amount of power comparable to a ratedpower of the heat pump.
 11. A heat pump operation method for use in asystem which includes a power generation device, an electric load whichoperates using power generated by the power generation device, and aheat pump which generates heat using the power generated by the powergeneration device, the method comprising: obtaining generated power,which is an amount of the power generated by the power generationdevice, load power, which is an amount of power consumed by the electricload, and surplus power, which is a difference between the generatedpower and the load power; and controlling an operation of the heat pumpby transmitting a power consumption command value to the heat pump atpredetermined time intervals, the power consumption command value beingan amount of power to be consumed by the heat pump for generating heat,wherein in the controlling, when the surplus power remains greater thanor equal to a first threshold value for a first period of time orlonger, which is a given prior period of time, measured from a presenttime, the power consumption command value at the present time iscalculated to follow the surplus power, when an amount of change in thesurplus power in a second period of time, which is a given prior periodof time, measured from the present time, and shorter than the firstperiod of time, is greater than a second threshold value, the powerconsumption command value previously calculated before the second periodof time is transmitted to the heat pump, such that the operation of theheat pump is controlled to generate heat using power that does notfollow the increase or decrease in the surplus power, and when theamount of change in the surplus power in the second period of time isless than or equal to the second threshold value, the power consumptioncommand value calculated at the present time is transmitted to the heatpump, such that the operation of the heat pump is controlled to generateheat using power that follows the increase or decrease in the surpluspower.
 12. The heat pump operation method according to claim 11, whereinwhen the power consumption command value is not obtained, controlparameters are calculated using a first control table, and when thepower consumption command value is obtained, control parameters arecalculated using a second control table which holds the powerconsumption command value.
 13. A heat pump system which includes a powergeneration device, an electric load which operates using power generatedby the power generation device, and a heat pump which generates heatusing the power generated by the power generation device, the heat pumpsystem comprising: an information obtainer configured to obtain, atpredetermined time intervals, generated power, which is an amount of thepower generated by the power generation device, load power, which is anamount of power consumed by the electric load, and surplus power, whichis a difference between the generated power and the load power; and anoperation controller configured to cause, at the predetermined timeintervals, the heat pump to generate heat using power determined basedon the surplus power, wherein the operation controller is furtherconfigured to, when the surplus power remains greater than or equal to apredetermined amount of power for a first period of time or longer,which is a given prior period of time, measured from a present time, andan amount of change in the surplus power in a second period of time,which is a given prior period of time, measured from the present time,and shorter than the first period of time, is equal to or smaller than apredetermined threshold value, control the operation of the heat pump togenerate heat using power that follows an increase or decrease in thesurplus power, and when the surplus power remains greater than or equalto the predetermined amount of power for the first period of time orlonger, and the amount of change in the surplus power in the secondperiod of time is greater than the predetermined threshold value,control the operation of the heat pump to generate heat using power thatdoes not follow the increase or decrease in the surplus power.
 14. Theheat pump system according to claim 13, wherein the operation controlleris configured to control the operation of the heat pump to generate heatusing power that does not follow the increase or decrease in the surpluspower, when the amount of change in the surplus power in the secondperiod of time is greater than the predetermined threshold value, and anamount of change in the load power is greater than an amount of changein the generated power.
 15. The heat pump system according to claim 13,wherein the operation controller is configured to control the operationof the heat pump to generate heat using the power approximatelycorresponding to the surplus power last obtained.
 16. The heat pumpsystem according to claim 13, wherein the operation controller isconfigured to control the operation of the heat pump to cause the heatpump to consume an amount of power adjusted to follow the surplus powerobtained, when a first condition is met, the first condition being thatthe surplus power remains greater than the predetermined amount of powerfor the first period of time.
 17. The heat pump system according toclaim 16, wherein the information obtainer is further configured toobtain, at the predetermined time intervals, an amount of heat in awater storage tank which stores hot water heated by the heat generatedby the heat pump, and the operation controller is configured to controlthe operation of the heat pump to cause the heat pump to consume theamount of power adjusted to follow the surplus power obtained at thepredetermined time intervals, when a second condition is met, inaddition to the first condition, the second condition being that theamount of heat in the water storage tank last obtained is less than orequal to a predetermined upper limit.
 18. The heat pump system accordingto claim 17, wherein the operation controller is configured to controlthe operation of the heat pump to cause the heat pump to consume theamount of power adjusted to follow the surplus power obtained at thepredetermined time intervals, when a third condition is met in additionto the first condition and the second condition, the third conditionbeing that the amount of heat in the water storage tank last obtained isgreater than a predetermined lower limit.
 19. The heat pump systemaccording to claim 13, further comprising: the heat pump which generatesheat; a water storage tank which stores hot water; and a heat exchangerwhich heats the hot water stored in the water storage tank with the heatgenerated by the heat pump, wherein the operation controller is furtherconfigured to: obtain an ambient temperature, which is a temperaturesurrounding the heat pump, an inlet water temperature, which is atemperature of the hot water flowing through the heat exchanger from thewater storage tank, and a heated water temperature, which is atemperature of the hot water supplied to the water storage tank from theheat exchanger; obtain control parameters, the control parameters (i)causing the heat pump to consume an amount of power adjusted to followthe surplus power obtained at the predetermined time intervals, and (ii)causing the heat pump to increase the temperature of the hot water fromthe inlet water temperature to the heated water temperature; and controlthe operation of the heat pump according to the obtained controlparameters.
 20. The heat pump system according to claim 19, wherein theoperation controller is configured to obtain the control parameterscorresponding to input information including the amount of powerconsumed by the heat pump, the ambient temperature, the inlet watertemperature, and the heated water temperature, by referring to a controltable holding the input information and the control parameterscorresponding to a combination of the input information.
 21. The heatpump system according to claim 20, wherein discrete values of the inputinformation are held in the control table, and the operation controlleris configured to, when the combination of the obtained input informationis not held in the control table, obtain the control parameters whichcorrespond to the combination of the obtained input information bylinear interpolation based on a plurality of the control parameters heldin the control table.
 22. The heat pump system according to claim 18,wherein the operation controller is configured to control the operationof the heat pump to cause the heat pump to consume an amount of powercomparable to a rated power of the heat pump when at least one of thefirst condition, the second condition, and the third condition is notmet.
 23. The heat pump system according to claim 13, further comprising:a heat pump hot water supply device which includes the heat pump, awater storage tank which stores hot water, a heat exchanger which heatsthe hot water stored in the water storage tank with the heat generatedby the heat pump, and a heat pump controller; and a heat pump controldevice which includes the information obtainer and the operationcontroller, and which is structurally separate from the heat pump hotwater supply device.
 24. A heat pump system comprising: a heat pump thatgenerates heat using power generated by a power generation device; and aheat pump control device that controls the heat pump, wherein the heatpump control device includes: an information obtainer configured toobtain an amount of the power generated by the power generation device,an amount of load power, and a status of a power grid; and an operationcontroller configured to calculate a power consumption command valueusing a surplus power calculated based on the amount of power generatedand the amount of load power, and the operation controller is furtherconfigured to: calculate the power consumption command value to followthe surplus power, when the surplus power remains greater than or equalto a first threshold value for a first period of time or longer, whichis a given prior period of time, measured from a present time; when anamount of change in the surplus power in a second period of time, whichis a given prior period of time, measured from the present time, andshorter than the first period of time, is greater than a secondthreshold value, transmit the power consumption command value previouslycalculated before the second period of time, to the heat pump, such thatthe operation of the heat pump is controlled to generate heat usingpower that does not follow the increase or decrease in the surpluspower; and when the amount of change in the surplus power in the secondperiod of time is less than or equal to the second threshold value,transmit the power consumption command value calculated at the presenttime to the heat pump, such that the operation of the heat pump iscontrolled to generate heat using power that follows the increase ordecrease in the surplus power.
 25. The heat pump system according toclaim 24, further comprising a power distribution device, wherein thepower distribution device transmits the amount of power generated by thepower generation device and the amount of load power to the informationobtainer included in the heat pump control device.
 26. The heat pumpsystem according to claim 24, further comprising a heat pump hot watersupply device including the heat pump and a heat pump controller,wherein the heat pump controller includes a first control table forcalculating operation parameters based on the power consumption commandvalue and a second control table for calculating operation controlparameters based on rated operation.